Artificial hip joints are known in which a femur implant is inserted into a bodily upper leg bone (femur), once a bodily joint head has been removed, and anchored or fastened in the bone. A spherical or partially spherical head, which may be attached to the femur implant or is fixedly connected to the femur implant can be accommodated by an abutment, such as, for example, a joint cavity, in the manner of a ball joint.
A typical femur implant can include a shaft made of, for example, titanium or plastic, and tapering conically downwards. The implant can be inserted into an upper leg bone once the bodily joint head has been removed. The shaft passes into a collar and a joint or femur head can be provided on the front side of the collar. The spatial position of the femur implant can be defined, for example, by determining the positions of the collar axis and the shaft axis. In general, femur implants designed in other ways, e.g. modularly, can also be used.
Seating the femur implant precisely in the upper leg bone is a decisive criterion for the success of implanting a hip joint. Even the smallest deviations can lead to increased wear and, therefore, to a reduced service life of the hip joint implant. If the femur implant is not positioned precisely in the upper leg bone, then the femur head of the femur implant arranged in the acetabular component or cavity can easily be dislocated, in particular, if sudden stresses or impacts act on the artificially inserted hip joint. If the hip joint components are not precisely positioned, suddenly occurring stresses can easily lead to the femur head or the collar axis of the femur implant colliding with either the rim of a corresponding cavity or soft tissue or a bone structure surrounding the implant. Correspondingly, precisely positioning the individual components of an artificial hip joint and in particular precisely positioning the femur implant is essential for a successful operation and a long service life of the joint as a whole.
A device and a method for implanting artificial joint components are known from U.S. Pat. No. 6,002,859. This proposes determining the position of the implant by simulation and tracking the hip, the hip joint cavity and the femur implant using an optical system. In this way, so-called targets are attached to bones and tools for inserting the artificial joint components. In one embodiment, the insertion of artificial, axially symmetrical hip joint components is described. However, the conventional process may be deficient when dealing with asymmetrical implants and other complicating factors.